What’s Vulnerable › Vulnerabilities

CVE-2026-77561: Tinyauth: Unauthenticated login attempts can trigger global login lockdown denial of service

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-21 · updated 2026-09-24
• Weakness: CWE-307

Description

Tinyauth is an authentication and authorization server. Prior to 5.1.0, an unauthenticated remote attacker can send POST /api/user/login requests with 257 distinct nonexistent usernames to fill MaxLoginAttemptRecords and activate a global login lockdown. internal/controller/user_controller.go loginHandler passes each attacker-controlled identifier to internal/service/auth_service.go RecordLoginAttempt, which invokes lockdownMode after the map reaches its cap. IsAccountLocked checks that global state before validating unrelated accounts, causing valid users to receive HTTP 429 until auth.loginTimeout expires, approximately 300 seconds by default. The attack can be repeated, but existing authenticated sessions are not invalidated. This issue is fixed in version 5.1.0.

Affected products

• tinyauthapp tinyauth: before 5.1.0

References

• https://github.com/tinyauthapp/tinyauth/commit/654b5cc436fc67865c1f55edf9ba9fbded50b74f
• https://github.com/tinyauthapp/tinyauth/commit/dade1e2c8f27a23df56ac216dcaf4b37081698e7
• https://github.com/tinyauthapp/tinyauth/pull/1008
• https://github.com/tinyauthapp/tinyauth/pull/943
• https://github.com/tinyauthapp/tinyauth/releases/tag/v5.1.0
• https://github.com/tinyauthapp/tinyauth/security/advisories/GHSA-9xhm-w3wj-xhqh
• https://github.com/tinyauthapp/tinyauth/security/advisories/GHSA-9xhm-w3wj-xhqh

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